JP2914075B2 - Method for producing (meth) acrylic acid ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a (meth) acrylic ester, and more particularly, to a method for producing a single compound without adding both an esterification catalyst and a polymerization inhibitor individually in large amounts. The present invention relates to a method for producing a (meth) acrylic acid ester, which can be esterified only by using a compound, and can be easily purified only by removing the compound after the reaction.

[0002]

2. Description of the Related Art (Meth) acrylic acid esters are used alone or in combination with other polymerizable monomers, oligomers, polymers, dyes, pigments, inorganic fillers, modifiers, and the like.
In the presence of radical initiators such as persulfates or azobis compounds, these initiators are easily polymerized by radicals generated by thermal decomposition or decomposition by irradiation with ultraviolet light or radiation, and have mechanical properties, heat resistance, weather resistance, and acid resistance. Produces a polymer with excellent chemical properties.

[0003] Further, since it is easily copolymerized with various compounds having a carbon-carbon double bond, it is possible to adjust the physical properties of the polymer according to the intended use, and it can be used for paints, inks, coating agents, adhesives, and adhesives. It is used in a wide range of fields as a raw material for agents, resins, rubbers, optical materials and the like.

A conventional method for producing a corresponding (meth) acrylic ester by subjecting (meth) acrylic acid and alcohol to a dehydration esterification reaction or a (meth) acrylic ester and alcohol to transesterification reaction. The following method is generally used.

That is, (meth) acrylic acid and an alcohol, or (meth) acrylic acid ester of a lower aliphatic alcohol and an alcohol are reacted by heating in the presence of an esterification catalyst and a polymerization inhibitor, The resulting water or lower alcohol is reacted with the solvent while azeotropically distilling it out of the reaction system. If the target (meth) acrylate is a low-boiling compound that can be distilled, purification is performed by distillation after completion of the reaction. If the compound has a high boiling point, the esterification catalyst and the polymerization inhibitor are removed by washing with an alkali or acid solution after completion of the same, followed by concentration to obtain the desired ester.

As the esterification catalyst, generally, sulfuric acid, phosphoric acid, methanesulfonic acid, benzenesulfonic acid, p
-Acid catalysts such as toluene sulfonic acid, strongly acidic cation exchange resins have been used.

[0007] As the polymerization inhibitor, hydroquinone, t
tert-butyl hydroquinone, methoquinone, 2,4-
Phenol compounds such as dimethyl-6-tert-butylphenol, catechol and tert-butylcatechol; amines such as phenothiazine, p-phenylenediamine and diphenylamine; copper such as copper dimethyldithiocarbamate, copper diethyldithiocarbamate and copper dibutyldithiocarbamate One or a mixture of compounds such as complexes has been used. Further, if necessary, one or a mixture of compounds such as powders of oxides, chlorides, sulfates, nitrates, and acetates of transition metals such as copper, manganese, and iron has been used in combination. .

[0008]

However, in any of the methods using these compounds, it is impossible to carry out the esterification reaction by using only the esterification catalyst or the polymerization inhibitor. Needed. For this reason, in the conventional reaction, a complicated process of separately adding the esterification catalyst and the polymerization inhibitor to the reaction system at the time of charging the raw materials before the reaction is required, and the amount of each added is sufficient to promote the esterification reaction. In order to obtain the polymerization preventing effect, there is a problem that the total amount must be large.

As a further serious problem, when the target (meth) acrylate is a high-boiling compound, after completion of the reaction, the esterification catalyst and polymerization inhibitor remaining in the system are replaced with excess alkali or acid. Although it must be removed by neutralization washing, the polymerization inhibitor is generally more difficult to neutralize and remove than the esterification catalyst and (meth) acrylic acid remaining after the reaction. It requires a large amount of alkali or acid solution that is sufficient to neutralize all, and also neutralizes the polymerization inhibitor, and generates a huge amount of wastewater, and makes it impossible to recover residual (meth) acrylic acid at all. There was a problem of becoming.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems relating to the conventional method for producing a (meth) acrylic acid ester, and as a result, dehydrated (meth) acrylic acid and alcohol. Esterification reaction, or (meth)
In the reaction of transesterifying the acrylate ester and the alcohol, the aromatic sulfonic acid other than the heterocyclic compound, a substituent selected from the group consisting of a lower alkyl group and a nitroso group, and a substituent adjacent to the substituent It has been found that these problems can be solved by using an aromatic sulfonic acid having a phenolic hydroxyl group,
The present invention has been completed.

That is, the present invention relates to an aromatic sulfonic acid other than a heterocyclic compound, which comprises a substituent selected from the group consisting of a lower alkyl group and a nitroso group, and a phenolic hydroxyl group adjacent to the substituent. In the presence of an aromatic sulfonic acid (A) (hereinafter, referred to as compound (A))
(Meth) acrylic acid (B ₁ ) and alcohol (C) are subjected to a dehydration esterification reaction or (meth) acrylic acid ester (B ₂ ) and alcohol (C) are subjected to transesterification reaction. ) A method for producing an acrylic ester.

The greatest feature of the present invention is that dehydration esterification of (meth) acrylic acid (B ₁ ) and transesterification of (meth) acrylic acid ester (B ₂ ) are possible only by using compound (A) alone. Therefore, there is no need to separately add the esterification catalyst and the polymerization inhibitor as in the prior art, and the amount of addition is smaller than that when separately added, that is, the same amount as the conventional esterification catalyst. Can be obtained only by the addition of the compound (A). Further, in the purification after the reaction, the purification can be performed only by neutralizing and removing only the compound (A), for example. A large-scale process of neutralizing and removing both the catalyst and the polymerization inhibitor, including the residual (meth) acrylic acid, with the alkali or acid solution of Data) is that it becomes possible recovery of acrylic acid.

Among the compounds (A) used in the present invention, aromatic sulfonic acids having a lower alkyl group and a phenolic hydroxyl group adjacent to the lower alkyl group include, for example,
2-methyl-1-phenol-4-sulfonic acid, 2-methyl-1-phenol-6-sulfonic acid, 2-tert
-Butyl-1-phenol-6-sulfonic acid, 2,6-
Dimethyl-1-phenol-4-sulfonic acid, 2,6-
Di-tert-butyl-1-phenol-6-sulfonic acid, 2,3-dimethyl-1-phenol-4-sulfonic acid, 2,3-dimethyl-1-phenol-6-sulfonic acid, 2,4-dimethyl -1-phenol-6-sulfonic acid, 2,5-dimethyl-1-phenol-4-sulfonic acid, 2,5-dimethyl-1-phenol-6-sulfonic acid, and the like.

Among the compounds (A) used in the present invention, examples of the aromatic sulfonic acid having a nitroso group and a phenolic hydroxyl group adjacent to the nitroso group include 2-nitroso-1-phenol-4-sulfonic acid. 2-nitroso-1-phenol-6-sulfonic acid, 2-nitroso-1
-Naphthol-4-sulfonic acid, 2-nitroso-1-naphthol-5-sulfonic acid, 2-nitroso-1-naphthol-6-sulfonic acid, 2-nitroso-1-naphthol-7-sulfonic acid, 2-nitroso -1-Naphthol-8
-Sulfonic acid, and the like.

Although not particularly required, conventional esterification catalysts such as alkylbenzene sulfonic acid and mineral acid, and transition metals and salts thereof can be used as long as they can be removed in the same manner as in the above compound (A). Conventional polymerization inhibitors and the like may be used in combination.

In the present invention, the amount of compound (A) added is
In general, the amount may be substantially the same as that of a conventional esterification catalyst.
20 parts by weight, preferably 0.5 to 10 parts by weight.

The (meth) acrylic acid (B) used in the present invention
₁ ) includes acrylic acid and methacrylic acid,
Examples of the (meth) acrylate (B ₂ ) include (meth) acrylates such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. ) Lower aliphatic alcohol esters of acrylic acid and the like. Among these, acrylic acid or methacrylic acid is preferred in the dehydration esterification reaction with alcohol, and methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate are preferred because the lower alcohol produced in the transesterification reaction has a low boiling point. Used.

As the alcohol (C), any compound can be used as long as it contains at least one alcoholic hydroxyl group. Such compounds include, for example, butyl alcohol, pentyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, isodecyl alcohol, 2-ethylhexyl alcohol, dodecyl alcohol, lauryl alcohol, palmityl alcohol, stearyl alcohol and the like. An alkyl-type alcohol;

Methoxyethyl alcohol, ethoxyethyl alcohol, butoxyethyl alcohol, methoxydiethylene glycol, ethoxydiethylene glycol,
Alkoxy-containing alcohols such as butoxydiethylene glycol, methoxytripropylene glycol, ethoxytripropylene glycol, butoxytripropylene glycol, methoxypolyethylene glycol and methoxypolypropylene glycol;

Cyclic alkyl alcohols such as cyclopentyl alcohol, cyclohexyl alcohol, cyclooctyl alcohol, methylcyclohexyl alcohol and ethylcyclohexyl alcohol; tetrafurfuryl alcohols such as tetrafurfuryl alcohol and methyltetrafurfuryl alcohol; Isobonyl alcohols such as bonyl alcohol and methyl isobonyl alcohol; aliphatic cyclic alcohols such as dicyclopentenyl alcohol, dicyclopentadienyl alcohol and dicyclopentenyloxyethyl alcohol;

Tert-butylaminoethyl alcohol, N, N-dimethylaminoethyl alcohol, N, N
Amino-containing alcohols such as diethylaminoethyl alcohol; fluorinated alcohols such as tetrafluoropropyl alcohol and heptadecafluorodecyl alcohol;
Benzyl group-containing alcohols such as benzyl alcohol;

Phenyl group-containing alcohols such as phenol and methylphenol; phenoxyethyl alcohol;
Phenoxy group-containing alcohols such as phenoxydiethylene glycol, phenoxytriethylene glycol, and phenoxyhexaethylene glycol; alkylene oxide-modified phosphoric acid alcohols; and hydroxyl groups such as ε-caprolactone-modified hydroxy alcohol and ε-caprolactone-modified tetrahydrofurfuryl alcohol.
Monohydric alcohols such as modified alcohols modified with caprolactone or alkylene oxide,

Alkyl alcohols containing hydroxyl groups at both ends such as 1,4-butanediol, 1,6-hexanediol, neopentyl glycol; ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol Alkylene glycol type alcohols such as propylene glycol and polypropylene glycol;
Ester-type double-ended hydroxyl group-containing alcohols such as ethylene glycol hydroxypivalate, diethylene glycol hydroxypivalate, and neopentyl glycol hydroxypivalate;

Trimethylolpropane, ethoxytrimethylolpropane, propoxytrimethylolpropane, ditrimethylolpropane, ethoxyditrimethylolpropane, propoxyditrimethylolpropane,
ε-caprolactone modified trimethylolpropane, ε-
Alcohols of trimethylolpropane and its derivatives, such as caprolactone-modified ditrimethylolpropane;

Pentaerythritol such as pentaerythritol, ethoxypentaerythritol, propoxypentaerythritol, dipentaerythritol, ethoxydipentaerythritol, propoxydipentaerythritol, ε-caprolactone-modified pentaerythritol, ε-caprolactone-modified dipentaerythritol and derivatives thereof. alcohol;

Trihydroxyisocyanurate, tris (hydroxyethyl) isocyanurate, tris (ethylene oxide-modified) isocyanurate, tris (propylene oxide-modified) isocyanurate, tris (ε-
Caprolactone modified) alcohols of isocyanurates and derivatives thereof, such as isocyanurates;

Heterocyclic derivatives such as furfuryl alcohol;
Ethylene oxide added bisphenol A, propylene oxide added bisphenol A, ethylene oxide added hydrogenated bisphenol A, propylene oxide added hydrogenated bisphenol A, ε-caprolactone modified bisphenol A, ethylene oxide added bisphenol S, propylene oxide added bisphenol S, ethylene oxide added Modified alcohols of bisphenol compounds such as hydrogenated bisphenol S, propylene oxide-added hydrogenated bisphenol S, ε-caprolactone-modified bisphenol S;

Examples include polyhydric alcohols such as glycerin, ethylene oxide-added glycerin, propylene oxide-added glycerin, and ε-captolactone-modified glycerin, but usable alcohols are not limited to these.

In the present invention, (meth) acrylic acid (B
₁ ) or (meth) acrylic acid ester (B ₂ ) is used in an amount of (meth) acrylic acid (B ₁ ) or (meth) acrylic acid ester (B) _per 1.0 hydroxyl groups in alcohol (C). ₂ ) can be varied widely from 0.03 to 30. However, when the alcohol to be removed after completion of the reaction can be distilled off by distillation, the amount is usually 0.03 to
The number is preferably 1.0 to 0.10 to 0.95 because the reaction progresses rapidly and there is no side reaction or generation of a colored substance. When the alcohol to be removed after the completion of the reaction cannot be distilled off, the number is usually 1.0 to 30. Among them, the reaction speed is particularly fast, and there is no side reaction or generation of a colored substance. Ten are preferred.

The dehydration esterification reaction or transesterification reaction in the present invention can be carried out in an organic solvent or in the absence of a solvent. Examples of the solvent include benzene, toluene, xylene, hexane, cyclohexane, heptane, octane, nonane, and methylcyclohexane. Etc., which can be phase-separated from water when mixed with water and azeotropic with water or a lower alcohol produced by transesterification, and have a boiling point of 6
Those in the range of 0 to 140 ° C are used. These solvents may be used alone or as a mixture, and may be used even if the solvent is not compatible with the starting material alcohol or cannot dissolve them. The addition amount is usually in the range of 0 to 300 parts by weight based on 100 parts by weight of the total of the component (A) and the component (B ₁ ) or the component (B ₂ ) and the component (C).

The reaction temperature in the present invention is usually from 40 to 20.
0 ° C., preferably from 60 to 120 ° C., and the reaction time is usually 0.5 to 20 hours, preferably 1 to 1 hour.
It is set to about 5 hours. Among them, the reaction temperature is most preferably 60 to 80 ° C. and the reaction time is most preferably 3 to 12 hours in that the desired (meth) acrylic acid ester can be obtained with high purity.

The reaction in the present invention can be carried out under atmospheric pressure, under reduced pressure in order to easily remove generated water or alcohol out of the reaction system, or under pressure in order to lower the boiling point of the solvent. It may be performed under pressure or under any pressure.

In the reaction of the present invention, (meth) acrylic acid (B ₁ ) or (meth) acrylic acid ester (B
₂ ) and to prevent polymerization of the resulting (meth) acrylate, oxygen or a mixture of oxygen and an inert gas, such as air or an oxygen / argon mixture, over the entire reaction time over the reaction solution and / or the reaction solution surface. The introduction of blowing improves the effect of preventing polymerization. At this time, it is preferable that oxygen or a mixture of oxygen and an inert gas is blown into the reaction solution so as to be as fine bubbles as possible, since water generated by the esterification reaction is promptly removed, and gas in the vicinity of the contact interface is preferable. Blowing into the phase is preferred from the viewpoint of preventing polymerization in the contact region between the reaction vessel surface and the reaction solution with the gas phase. In any case, it is preferable to perform the blowing into the system because it can prevent polymerization during the reaction, whether in a liquid or a gas phase, and works in a direction to promote the reaction.

The removal of compound (A) in the present invention can be carried out by various purification methods such as neutralization washing with alkali, adsorption, reprecipitation and, if necessary, filtration. Further, a method in which filtration is further combined as necessary is preferable.

In the neutralization washing with an alkali, it is not necessary to neutralize all of the esterification catalyst, the residual acid, and the polymerization inhibitor as in the conventional method. 1.0 to 1.5 times the amount of alkali, preferably 1.0 to 1.5 times the theoretical neutralization equivalent to (A).
It is sufficient to use 1.2 times the amount of alkali. Similarly, in the adsorption, it is only necessary to use the adsorbent in an amount capable of adsorbing only the compound (A) preferentially and completely removing the same.
When other esterification catalysts are used in combination with the compound (A), it goes without saying that a neutralization amount of alkali relative to the total amount is required.

As the alkali usable for the neutralization washing,
There is no particular limitation as long as it is a water-soluble alkali, but for example, alkali metal hydroxide, alkali metal carbonate, alkali metal phosphate and the like are preferably used, and sodium hydroxide, potassium hydroxide, carbonate Sodium, potassium carbonate, trisodium phosphate and tripotassium phosphate are particularly preferred.

As the adsorbent that can be used in the adsorption treatment, any substance can be used as long as it can efficiently adsorb the esterification catalyst having a polymerization preventing function. Examples of the adsorbent include clays such as activated clay and acid clay. Silica gels such as zeolites, hydrotalcites, silica gel, silica alumina gel, silica magnesia gel, alumina and its modified products, activated carbon, oxides of alkaline earth metals such as magnesium oxide, calcium oxide, magnesium carbonate, calcium carbonate And alkaline earth metal hydroxides such as magnesium hydroxide and calcium hydroxide; alkaline earth metal phosphates such as magnesium phosphate and calcium phosphate; and Group 3 such as zinc oxide. Metal oxides,
An ion exchange resin, an adsorption resin or the like can be used. These can be used alone or in combination of two or more. The method of use may be either a batch method or a column method.

The method of the filtration treatment is not particularly limited, and any commonly used gravity filtration, pressure filtration, vacuum filtration, centrifugal filtration, etc. can be used. Either can be used.

In the method for producing a (meth) acrylate according to the present invention, after the removal of the esterification catalyst having a polymerization preventing function, the ester remained in the solution by extraction or distillation as required. It is also possible to collect (meth) acrylic acid or (meth) acrylic acid ester and remove coloring components and reaction by-products by methods such as adsorption, reprecipitation and filtration.

The purified (meth) acrylic acid ester thus obtained has the property of being easily polymerized, so that it can be used immediately in any polymerization step, or if it is stored, a polymerization inhibitor is added. Is preferably added.
In this case, the type of polymerization inhibitor is hydroquinone,
Methoquinone is mainly used, but methoquinone is particularly preferred in that there is no denaturation coloring. The amount of addition depends on the type of the (meth) acrylic ester obtained, but is usually 5 to 5%.
000 ppm, preferably 50 to 2500 ppm.

[0041]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the content of the present invention is not limited to the examples. Further, the following percentages are based on weight unless otherwise specified.

The purification methods (1) to (4) performed in Examples and Comparative Examples, the removal rate of the compound (A) or the esterification catalyst, the removal rate of the polymerization inhibitor, the presence or absence of the polymer,
The methods for determining the recovered amount of acrylic acid, the yield of (meth) acrylic acid ester and the conversion rate of alcohol reaction are shown below.

Purification method (1): a method of filtering after neutralization washing, and adding 1 equivalent to the neutralization equivalent of compound (A) to this reaction diluent.
A 20% aqueous sodium hydroxide solution was added thereto, and the mixture was stirred for 20 minutes, and then allowed to stand for 4 hours to separate an upper layer solution. Then, 0.08 g of methoquinone was added to the upper layer solution, and the mixture was heated to 70 ° C., and the solvent was first distilled and recovered under reduced pressure, and the residual (meth) acrylic acid was recovered by distillation under high reduced pressure. Filtration of dust mixed during each operation as a material to target (meta)
An acrylic ester was obtained.

Purification method (2): a method of filtering after continuous adsorption with an adsorption column, and then filtering this reaction diluent with an acid clay column having an inner diameter of 70 mmφ and a length of 300 mm [granular acid clay A-36: manufactured by Nippon Activated Clay Co., Ltd. Was passed through at a flow rate of 250 ml / hr, and after the entire solution had passed, the column was washed with 1000 ml of a diluting solvent, and this washing solution was added to the previously passed reaction diluent. Then, 0.08 g of methquinone was added to the solution, and the mixture was heated to 70 ° C., and the solvent was first distilled and recovered under reduced pressure, and the residual (meth) acrylic acid was recovered by distillation under high reduced pressure. By filtering dust mixed during each operation, the desired (meth) acrylate was obtained.

Purification method (3): a method of performing batch adsorption treatment with an adsorbent and then filtering 10 g of activated clay was added to the reaction diluent, and suction filtration was performed using diatomaceous earth as a filter aid. Then, 0.08 g of methquinone was added to the solution, and the mixture was heated to 70 ° C., and the solvent was first distilled and recovered under reduced pressure, and the residual (meth) acrylic acid was recovered by distillation under high reduced pressure. By filtering dust mixed during each operation, the desired (meth) acrylate was obtained.

Purification method (4): a method of filtering after washing with pure water, adding pure water equivalent to 10% by weight of the reaction solution to the reaction diluent, stirring for 20 minutes, and allowing to stand for 4 hours, The upper solution was separated. This washing operation was repeated three times. Then, 0.08 g of methoquinone was added to the upper layer solution, and the mixture was heated to 70 ° C., and the solvent was first distilled off under reduced pressure, and the remaining (meth) acrylic acid was recovered by distillation under high reduced pressure. The dust mixed during each operation was filtered to obtain the desired (meth) acrylate.

Purification method (5): after neutralization washing with a large amount of alkali,
Conventional method of filtration The reaction diluent was added to a 10% aqueous sodium hydroxide solution 550.
g, and then twice with 550 g of pure water.
Then, about 0.08 g of methoquinone was added to this solution,
First, the solvent is reduced to a reduced pressure by heating to 70 ° C., and the remaining (meth) acrylic acid is distilled and recovered under a high reduced pressure, and diatomaceous earth is used as a filter aid to filter dust and the like mixed during each operation. (Meth) acrylic acid ester was obtained.

-Compound (A) or esterification catalyst removal rate Calculated from the content of compound (A) or esterification catalyst in the reaction solution before and after purification measured by ion chromatography. -Polymerization inhibitor removal rate Calculated from the content of the polymerization inhibitor in the reaction solution before and after purification measured with an ultraviolet / visible absorption spectrophotometer.

-Presence or absence of polymer To the reaction solution after the reaction, 4 volumes of methyl alcohol was added, and the presence or absence of the polymer was determined by the presence or absence of formation of cloudiness. -Recovered amount of (meth) acrylic acid The weight of (meth) acrylic acid obtained by vacuum distillation of the reaction solution after completion of the reaction was determined.

(Yield of (meth) acrylate) Calculated from the amount of (meth) acrylate after purification and the theoretical yield. -Alcohol reaction conversion The amount of alcohol before and after the reaction was measured by gas chromatography and calculated. -(Meth) acrylic acid ester purity The purity of the (meth) acrylic acid ester after purification by GPC measurement [the content of the (meth) acrylic acid ester monomer in the purified product containing monomers and multimers, etc.] I asked.

Examples 1 to 5 and Comparative Examples 1 and 2 In a 1-liter glass four-necked flask equipped with a reflux condenser, a water separator, an air inlet tube, a thermometer, a stirrer, and a dropping funnel, the amounts shown in Table 1 were used. Compound (A) having both a polymerization preventing function and an esterification catalytic function, alcohol, (meth) acrylic acid and a solvent were charged. Next, while air was blown into the flask at a rate of 20 ml / min, the mixture was heated using a hot water bath, and the solvent and by-produced water began to azeotrope while stirring the internal solution. Example 1
3 and Comparative Examples 1-2 under atmospheric pressure and Examples 4-5
In Table 2, the solvent was refluxed while the water was azeotropically removed by a water separator under the reduced pressure shown in Table 2, and reacted at the reaction temperature shown in Tables 1-2. Immediately after the completion of the reaction, the dilution solvent shown in Tables 1 and 2 was added, and the mixture was cooled to room temperature. The reaction diluent was purified using the purification method shown in Tables 1 and 2, and then compound (A) or esterification The removal rate of the catalyst, the removal rate of the polymerization inhibitor, the presence or absence of the polymer, the recovered amount of (meth) acrylic acid, the yield of (meth) acrylate and the conversion rate of alcohol reaction were determined. The results are shown in Tables 1 and 2. To remove 100% of the polymerization inhibitor in Comparative Example 1, neutralization washing with a large amount of alkali was required.

[0052]

[Table 1] In the above table, “*” indicates “unrecoverable”.

[0053]

[Table 2]

The compounds (A) 1 to 3 in Tables 1 and 2 and Table 3 below are as shown below. In each table, “Compound (A) catalyst removal rate (%)” means “Compound (A)
Or the esterification catalyst removal rate ”. Compound (A) -1: 2-methyl-1-phenol-4-sulfonic acid −２-2: 2-nitroso-1-phenol-4-sulfonic acid −３-3: 2-nitroso-1-naphthol-4-sulfone acid

Examples 6 to 8 and Comparative Example 3 1 liter equipped with a rectification tower, a reflux condenser with a solenoid valve equipped with a temperature sensor, an air inlet tube, a thermometer, a stirrer, and a dropping funnel
A glass four-necked flask was charged with the amounts of the compound (A), alcohol and methyl (meth) acrylate having both the function of preventing polymerization and the function of esterification catalyst as shown in Table 3. Next, the inner solution was stirred and heated using a hot water bath while blowing air into the flask at a rate of 20 ml / min. When the top temperature of the rectification column is set to the temperature shown in Table 3, an azeotropic solution of methyl (meth) acrylate and by-produced methyl alcohol is distilled at a temperature lower than the set temperature, and the temperature becomes higher than the set temperature. Was completely refluxed. The reaction was carried out at the reaction temperature shown in Table 3 while separating the above azeotropic mixture for the reaction time shown in Table 3 after the methyl (meth) acrylate and methyl alcohol started azeotropic. After completion of the reaction, the mixture was heated to 70 ° C. under reduced pressure, and residual methyl (meth) acrylate was recovered by distillation. Next, Table 3
The reaction diluent was purified by the purification method shown in Table 3, and then the compound (A) or esterification catalyst removal rate, polymerization inhibitor removal rate, polymer , The (meth) acrylate yield and the alcohol conversion were determined. Table 3 shows the results. To remove 100% of the polymerization inhibitor in Comparative Example 3, neutralization washing with a large amount of alkali was required.

[0056]

[Table 3]

[0057]

According to the production method of the present invention, the desired (meth) acrylic acid can be obtained by simply adding the compound (A) having both the function of preventing polymerization and the function of esterification catalyst to a conventional esterification catalyst. It is possible to obtain an ester and further purify the compound only by removing the compound (A) alone, and to remove all the esterification catalyst and polymerization inhibitor including the residual (meth) acrylic acid as in the conventional case. Not only can a large-scale process be remarkably reduced in scale, but also the recovery of residual (meth) acrylic acid becomes possible.

Continuation of the front page (56) References JP-A-54-59221 (JP, A) JP-A-60-81203 (JP, A) JP-A-63-23839 (JP, A) JP-B-44-24578 (JP) , B1) International Publication 90/7487 (WO, A1) (58) Fields investigated (Int. Cl. ⁶ , DB name) C07C 69/54 C07C 67/03 C07C 67/08

Claims (1)

(57) [Claims] 1. An aromatic sulfonic acid other than a heterocyclic compound
A group consisting of a lower alkyl group and a nitroso group
A substituent selected from the group and a phenolic group adjacent to the substituent.
In the presence of an aromatic sulfonic acid having a hydroxyl group (A),
(Meth) acrylic acid (B ₁ ) and alcohol (C) are subjected to a dehydration esterification reaction or (meth) acrylic acid ester (B ₂ ) and alcohol (C) are subjected to transesterification reaction. ) A process for producing acrylic esters .